Ok Im, not a tube god and do not profess to have great knowledge in the field of tube amplifiers. That said, I have just come into a fairly beat Dynaco st-35. There are no tubes in it and the circuit boards look to have been hot for a long time but transformers look OK.

My question is this: Is it worth restoring this thing back to it's original circuitry or has time left this design so far behind it's better to just scrap it for parts (transformers) and build something with a more modern topology. On the one hand I could end up with nice classic amp. On the other hand if it does not sound that great why bother. There seem to be allot of designs around using dynaco transformers with more up to date designs. Is there any sense of agreement on what to do with an old st-35

greetings, I think either approach is valid but to cover yourself you could build a new chassis and try a different topology using the tfmrs (which were always considered very good) so you can always pop them back in the st35. I think you can do much better sound wise t han the original circuits using a seperate phase slpitter rather than that triode/ pentode 7199 tube which while it worked quite well was proobably a cost saving measure in the first place. There is plenty of info on the net and I remeber a site where a guy had a step by step process of doing what you are thinking except he got his tfmrs from a sca35 but same diff. Especially that it a is a beat up one in the first place I think, to coin a well used phrase" out of the ashes the pheonix rises"
cheers and good luck cheers fergs

You owe it to yourself to at least get it operating condition, listen to it, and decide for yourself what you will do. (and I'll bet you'll be quite surprised!) It's not a powerhouse, however, and requires speakers of , at least moderate efficiency. The 17.5 Watts/ch rating is a little bit of a stretch! The output transformers are considered among the best ever built and are in demand! The power transformer is stressed fairly hard and has been know to fail from time to time, although it's not a problem, as improved replacements are easily available. Give it a try!

Thanks to everyone who replied. I suppose I should have guessed before hand that I woulf get near an even split on the rebuild verse gut question. It looks like a new populated set of st-35 boards ould set me back about $100 and and the diytube boards would be about $ 130. But I loose another $35 replacing the 3 section electrolytic with a similar unit (I just guessng its bad but its hard not to believe it shouldn't be replaced anyway).

The new pc board then requires a new chasis for about $80 but the rebuilt original will still be sitting on a chasis which clearly didn't have enough ventilation. Overall it still seems about equal what the best thing to do is.................

Any thoughts on which 6BQ5's represent a decent deal? Seems silly to put premium tubes in a low end amplifier.

PS fist job for this thing if I ever get it working will be to take over driving my old Stax ESL headphones

Thnx again to all who replied. Looks like a quad of JJ EL-84's and some deep thought are in order. Since I work in an optoelectronics releated field I will have to walk the "Red Light District" thread back to see what a dozen or so LEDs are doing in a amplifier full of fire bottles.